1. Field of the Invention
The present invention relates generally to an adjustable shelving system, and more particularly to an adjustable shelving system that uses plastic shelves. The use of plastic shelves is advantageous in many applications because they resist corrosion in otherwise corrosive environments. Plastic shelves also enhance design freedom while providing a sturdy structure. The adjustable plastic shelving system of the present invention is readily assembled and disassembled without tools to facilitate shipping, storage and cleaning.
2. Description of the Prior Art
Adjustable shelving systems are well known in the art. For example, U.S. Pat. Nos. 3,523,508 (Maslow) and 3,757,705 (Maslow) disclose such systems that have met with great commercial success under the trademark SUPER ERECTA SHELF of Applicant's Assignee, InterMetro Industries Corporation.
U.S. Pat. No. 3,523,508 discloses an adjustable shelving system comprising a formed-wire shelf component having a frustro-conically shaped collar at each corner for receiving a support post. Each collar tapers outwardly toward its lower extremity when viewed in normal use. Generally cylindrical support posts, each having a plurality of uniformly spaced annular grooves formed in its outer surface, are secured to the shelf by a mounting assembly. Each mounting assembly comprises at least two separate, complementary, conically-shaped mounting members which are joined about and at least partially surround the support post to define a sleeve. The outer surface of each sleeve is also frustro-conically shaped. Thus, the mounting sleeve is thickest at its bottom portion. The sleeves are sized to fit snugly within the shelf collars. A rib formed on an inside surface of each sleeve is sized to engage the annular groove formed on the support post.
To assemble the shelving system, sleeves are first placed about each support post such that the rib formed on the inside surface of each sleeve engages an appropriate groove in the support post. The support post with the sleeves mounted thereon is then passed through one respective collar at a corner of each shelf. The collars, sleeves and posts firmly engage each other due to their relative respective sizes. When all support posts are inserted, the shelving system is placed in position and ready for use. As the load on the shelf increases, a wedging action between the collars and sleeves produces a radially inwardly directed force exerted by the collars on the sleeves. This radially inwardly directed force securely locks the sleeves onto the posts.
U.S. Pat. No. 3,757,705 discloses an adjustable shelving system similar to that disclosed in U.S. Pat. No. 3,523,508, and further features the frustro-conical collar at each corner of the formed-wire shelf having a split wall. The split wall permits partial elastic lateral expansion within the collar to account for tolerance differences between the collar and the frustro-conical sleeve.
The shelving systems described above typically use plastic or metal materials for the posts and tapered sleeves, while the shelf is made of metal wire and the collar is made of metal sheet.
It is also known to use either solid or slotted plastic shelves in systems having components such as described above. Plastic shelves are lower in cost and weight. Such a system is shown, for example, in U.S. Pat. No. 4,964,350 (Kolvites) also assigned to InterMetro Industries.
However, plastic shelves have certain disadvantages. More particularly, the salient feature of the Maslow patents discussed above lies in the frustro-conical, or tapered, shape of the sleeve carried on the support post and the complementary shaped collar in the shelf. As the load supported by the shelve increases, the rigidity of the shelving system improves due to the noted wedging action between the tapered sleeve and complementary-shaped collar. However, that wedging action also produces a radially outwardly directed force exerted by the tapered sleeves on each collar of the shelf. Like the radially-inwardly directed force, the outwardly directed force increases as the load on the shelf increases. This outwardly directed force can cause a plastic shelf formed with plastic collars to crack or burst at its corners and fail. Therefore, further improvements in plastic shelf construction are needed.